The routine may be called by the names d02uzf or nagf_ode_bvp_ps_lin_cheb_eval.
d02uzf returns the value, , of the th Chebyshev polynomial evaluated at a point ; that is, .
Trefethen L N (2000) Spectral Methods in MATLAB SIAM
1: – IntegerInput
On entry: the order of the Chebyshev polynomial.
2: – Real (Kind=nag_wp)Input
On entry: the point at which to evaluate the polynomial.
3: – Real (Kind=nag_wp)Output
On exit: the value, , of the Chebyshev polynomial order evaluated at .
4: – IntegerInput/Output
On entry: ifail must be set to , or to set behaviour on detection of an error; these values have no effect when no error is detected.
A value of causes the printing of an error message and program execution will be halted; otherwise program execution continues. A value of means that an error message is printed while a value of means that it is not.
If halting is not appropriate, the value or is recommended. If message printing is undesirable, then the value is recommended. Otherwise, the value is recommended. When the value or is used it is essential to test the value of ifail on exit.
On exit: unless the routine detects an error or a warning has been flagged (see Section 6).
6Error Indicators and Warnings
If on entry or , explanatory error messages are output on the current error message unit (as defined by x04aaf).
Errors or warnings detected by the routine:
On entry, .
On entry, .
An unexpected error has been triggered by this routine. Please
See Section 7 in the Introduction to the NAG Library FL Interface for further information.
Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library FL Interface for further information.
Dynamic memory allocation failed.
See Section 9 in the Introduction to the NAG Library FL Interface for further information.
The accuracy should be close to machine precision.
8Parallelism and Performance
Background information to multithreading can be found in the Multithreading documentation.
d02uzf is not threaded in any implementation.
A set of Chebyshev coefficients is obtained for the function defined on using d02ucf. At each of a set of new grid points in the domain of the function d02uzf is used to evaluate each Chebshev polynomial in the series representation. The values obtained are multiplied to the Chebyshev coefficients and summed to obtain approximations to the given function at the new grid points.